1. Field of the Invention
The present invention relates to flow responsive devices, and in a more particular sense, to switches that are magnetically controlled, and are actuated as a response to fluid pressure within an adjacent conduit.
2. Description of the Prior Art
The general concept of having a magnetically controlled switch responsive to a flow condition within a conduit is known. In U.S. Pat. No. 3,327,079 issued to Widl it is proposed, by way of example, to utilize a permanent magnet bodily shifted by the pressure fluid to actuate a reed switch. Other patents showing the concept of magnets (though within the conduit itself) are U.S. Pat. Nos. 3,446,986 to Cox and 4,181,835 to Stadlet et al., both of which disclose magnets movable by a pressure fluid to act upon a switch mounted adjacent the conduit.
In U.S. Pat. Nos. 3,766,779 to Hoffman and 4,071,725 to Smith et al., it is proposed to utilize magnetically attractable pistons movable within a conduit according to the changing condition of fluid flow therein. In U.S. Pat. No. 4,071,725 the piston moves to a position adjacent a magnet to shift the magnet and in this way to operate a switch. In U.S. Pat. No. 3,766,779 a permanent magnet is provided, affixed to the piston to act upon a slave magnet.
While in many instances the switches disclosed in the mentioned patents are operable efficiently for their intended purposes, there remains room for improvement, in that it is desirable to swiftly and easily adjust the relative positions of the components of the device, so as to correspondingly select, in an adjustable fashion, the point at which the adjacent switch will close or open, as the case may be. And, it is also desirable to provide, in a device of this type, components that can be readily modified or interchanged, either at installation or thereafter, in such a manner as to adjust the fluid pressure required to actuate the switch.